Make sure no one else within your company has activated your BIM 360 contract.

Make sure your company doesn't already have a BIM 360 site. Ask other users if they have already created a BIM 360 site.

You should've gotten an email from Autodesk asking you to activate your BIM 360 Design contract. But if you didn't or you don't know, you can verify by going to this link: Activate your new BIM 360 Design account, enter your information and contract number. If you have already activated it or your email address is already associated with the BIM 360 website you will see in red;

"This contract number has already been used to create a BIM 360 account. Try signing into BIM 360" or "This email has already been used to create an account. Try signing in to BIM 360".

You will need to try signing into the BIM 360 website at: https://admin.b360.autodesk.com. If you cannot access the website because it keeps looping you to the sign in page or get a message that "You're not enterprise admin user"

Solution:

You will need do one of the following to get this issue fixed:

Contact your Autodesk reseller

Send an email to Autodesk at bim360success@autodesk.com letting them know you are not able to access the BIM 360 site or activate your contract number.